Errr, quite possibly. Fitting a higher flow fuel pump and not adjusting the
fuel map (by mapping the ECU or using an AFC) will richen the mixture.
An overly rich mixture will rob you of power; infact a mate
on the supra site nearly lost an engine due to running too rich after a
rogue tuning company f11cked up the mapping of his fuel computer !
An ultra rich mixture washes oil from the bores.....ouch...!
Even worse, the parts may not have been fitted correctly and you now
have a lean mixture.....only way you'll find out is by taking your
car to a rolling road centre and get your mixture checked....ASAP.
Just to give you an example, my car ran 336bhp with an a/f of 12.1,
then we richened it up a little to 11.5 and it ran 332bhp.
Justin